The present disclosure provides compositions and methods for acidizing treatment fluids comprising hydrofluoric acid.
Treatment fluids can be used in a variety of subterranean treatment operations. Such treatment operations can include, without limitation, drilling operations, stimulation operations, production operations, sand control treatments, and the like. As used herein, the terms “treat,” “treatment,” “treating,” and grammatical equivalents thereof refer to any subterranean operation that uses a fluid in conjunction with achieving a desired function and/or for a desired purpose. Use of these terms does not imply any particular action by the treatment fluid. Illustrative treatment operations can include, for example, fracturing operations, gravel packing operations, acidizing operations, scale dissolution and removal, consolidation operations, and the like.
In acidizing operations, a subterranean formation containing an acid-soluble material can be treated with an acid to dissolve at least a portion of the material. Formation components of the formation matrix may comprise the acid-soluble material in some cases. In other cases, the acid-soluble material may have been deliberately introduced into the subterranean formation in conjunction with a stimulation operation (e.g., proppant particulates). Illustrative examples of formation components that may be dissolved by an acid include, for example, carbonates, silicates, and aluminosilicates. Dissolution of these formation components can desirably open voids and conductive flow pathways in the formation that can improve the formation's rate of hydrocarbon production, for example. In a similar motif, acidization may be used to remove like types of precipitation damage that can be present in the formation.
Carbonate formations contain minerals that comprise a carbonate anion (e.g., calcite). When acidizing a carbonate formation, the acidity of the treatment fluid alone can be sufficient to solubilize the formation components. Both mineral acids (e.g., hydrochloric acid) and organic acids (e.g., acetic and formic acids) can be used to treat a carbonate formation, often with similar degrees of success.
Siliceous formations can include minerals such as, for example, zeolites, clays, and feldspars. Most sandstone formations contain about 40% to about 98% sand quartz particles (i.e., silica), bonded together by various amounts of cementing material including carbonates (e.g., calcite), aluminosilicates, and other silicates. As used herein, the term “siliceous” refers to a substance having the characteristics of silica, including silicates and/or aluminosilicates.
Acidizing a siliceous formation (e.g., a sandstone formation or a clay-containing formation) may present more difficulties than acidizing a carbonate formation. Specifically, the treatment of a siliceous formation with the treatment fluids commonly used for acidizing a carbonate formation may have little effect because most mineral acids and organic acids do not effectively react with siliceous materials. In contrast to most mineral acids and organic acids, hydrofluoric acid (HF) can react readily with siliceous materials to produce soluble substances.
The use of HF, however, can be detrimental to certain types of equipment. In particular, HF is especially corrosive to sensitive metallurgic grades, such as titanium. As such, it is generally undesirable to expose titanium alloys to HF acidizing compositions.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.